Candle-foot photometer.



CANDLE FOOT PEOTGMETER.

APPLICATION FILED JAH. 25, 190?.

'afuented wuellHL Egadi.

a any@ s PYJVALIIJJER. Di. RYAN, OF LYNN, MASSACHUSETTS, .SSIGNOR TG GENERAL ELECTR COMPANY, A CORORATIGN GF NEW' YORK.

CANDLE-FOGT PHGTOMETER.

To all whom t may concern:

Be it known that l, VVnL'rnn Dlt. RYAN, a subject oit the King ot Great Britain, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful improvements in Candle-Foot Photometers, of which the following is specification.

My present invention relates to device tor measuring light intensity.

The apparatus is portable and has the advantage oit giving the readings directly.

rlhe details of my invention will be better understood by reference to the accompanying drawings forming a part of this speciiication.

Figure l is an elevation of the photometer with one side removed and with certain portions broken away; F ig. 2 is a plan view of the photometer with a portion of the top broken away; Fig. 3 is an end elevation from the lamp end; Fig. 4t is an elevation from the opposite direction with the end of the box removed; Fig. 5 shows one form oit light comparing means; and Fig. G shows a n1odifcation of the same.

rlhe photometer consists of a rectangular, light-proof box with a movable standard lamp at one end and light comparing means at the other. rilhe side walls ot the box are provided with two strips l and 2 forming a guide way in which a platform 3 is movable lengthwise of the box. This platform carries the calibrated or standard lamp 4 by which comparisons are made, and also a shield 4 arranged directly behind the lamp and practically filling the entire crosssection of the box. This shield tends to maintain constant reflection. Movement ot the platform is effected by .means ott a tube 5 projecting through the front of the box. The tube serves as a. conduit tor the lamp circuit and also carries on its outer surface a series ot figures properly arranged to give direct reading in candle feet. To insure proper comparison between the standard .lamp il and the light under measurement, the front of the photometer is provided with light comparing means ot the form shown in Fig. 5, or of the modilied l'orm shown in Fig. 6.

The device shown in Fig. 5 comprises two rectangular blocks 6 and of paraiiin, opalized glass or similar didusing material.

Specification ot Letters Eatent.

Application filed January 25, i907.

Each block is covered with an opaque coating, except for one side, and a small rectangular slot near one of the edges. ln the surfaces which are not opaque are indicated by the referencev numerals 8 and 9 for block 6 and l0 and ll Jier bloclr 7. Tlhen these blocks are arranged for use in the photometer, the light-transinitting sur tace l0 faces the standard lamp dl, while the light-transmitting surface 8 faces upward or in the direction of the light to be measured. Light from the standard lamp passes into paraiiin block and illuminates the slot l1 with an intensity depending on the position of the standard lamp. Similarly, the illumination otl slot 9 depends on the intensity of the light entering bloclr 6 by way ot the ligl'it-transinitting surface 8. it the illumination ot slot 9 is not the same as that ot slot ll, the standard lamp may be moved toward or away from the blocks until a balance is obtained. '.ihe reading on the bar 5 gives directly the numerical value of the illumination.

rllhe modified form ot' light comparing bloclr shown in Fig. 6 comprises two prismatic blocks separated by an opaque surface. The uppermost body or prism l2 is provided with a light transmitting surface 13 and a slot let, while the other prism is provided with a light transmitting surface l5 and a slot 1G. This comparing means may be mounted in the photometer as shown in Fig. l by supporting it on a suit-able rectangular block 17. A diaphragm 18 may be inserted between the paratlin blocks and the standard lamp and may have a restricted opening 19 as indicated in Fig. t. ri`his diaphragm serves to cut down the light transmitted trom the standard lamp to the parailin blocks.

lllhen the light comparing blocks areinade oi opalized glass l prefer to have the er; posed surface, which receives the light in the room, iinely ground so as to obviate errors which might be introduced because of the angularity of the light.

l,What l claim as new and desire to secure by Letters atent. or' the United States, is:

l. In a portable photometer, light oomparing means comprising blocks oi diffusing material, opaque coverings for said blocks with light transmitting openings through which light may be received from separate Sources, and smaller openings permitting comparison of the relative intensity of illumination by said sources.

2. In a portable photometer, light comparing means comprising blocks of diiusing material, opaque Covering for portions of said blocks, light transmitting surfaces at right angles to each other and a third surface at right angles to both and containing light transmitting slots illuminated respectivelyv through Said light transn'iitting` surfaces.

3; In a portable photometer, the combination of a box, a standard lamp movablT mounted therein, a shield arranged directly behind said lamp in xed relation thereto, and means for comparing the illumination from said standard lamp with the general illumination of the space surrounding said box.

n a portable photometer, light comparing means eomprising adjacent prismatic blocks of diifusing material, opaque and light transmitting surfaces therefor, and slots in said opaque surfaces permitt-ing comparison of the illumination of the light transmitting surfaces.

In Witness whereof, I have hereunto set my hand this twenty-second day of J an nary, 190?.

. WALTER DA. RYAN. lfilitnesses JOHN A. MGMANUS, Jr., PHILIP F. HARRINGTON. 

